The Dosimetry Group provides support to the Department of Homeland Security (DHS) in their evaluation of cargo and vehicle inspection systems. Our support for these programs falls into two categories. The first activity is developing and implementing methods to test the performance of these systems. The second is developing and implementing methods to perform radiation dosimetry in and around these high-energy systems.
The American National Standards Institute (ANSI) standard for the image quality indicators of non-intrusive cargo and vehicle inspection systems, ANSI N42.46, was previously developed through a series of meetings hosted by NIST. NIST has conducted and analyzed the results of tests using this standard. The results of these tests and the experience accumulated by others in applying the standard are highly significant in the development of the next version of the standard currently under development with facilitation by NIST staff. The highly-collimated, high-energy photon beams increasingly utilized in non-intrusive inspection (NII) systems present dosimetry challenges, as they are of markedly different character compared to those employed in the past. Hence, the usual methods used to perform dosimetry must be revised. We have developed methodologies to perform measurements of dose to drivers of conveyances under inspection, to evaluate dose to cargo and inadvertent occupants of the conveyance and to determine the radiation footprint of these systems. We participate in the development of the Health Physics Society/ American National Standards Institute (HPS/ANSI N43.16) in order to bring these methods into this consensus standard for radiation dosimetry around such systems.